US8066254B2 - Mold for producing silica crucible - Google Patents

Mold for producing silica crucible Download PDF

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Publication number
US8066254B2
US8066254B2 US12/688,452 US68845210A US8066254B2 US 8066254 B2 US8066254 B2 US 8066254B2 US 68845210 A US68845210 A US 68845210A US 8066254 B2 US8066254 B2 US 8066254B2
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US
United States
Prior art keywords
mold
silica
crucible
rim member
silica crucible
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Expired - Fee Related, expires
Application number
US12/688,452
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English (en)
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US20100178374A1 (en
Inventor
Takuma Yoshioka
Masaki Morikawa
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Sumco Corp
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Japan Super Quartz Corp
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Assigned to JAPAN SUPER QUARTZ CORPORATION reassignment JAPAN SUPER QUARTZ CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MORIKAWA, MASAKI, YOSHIOKA, TAKUMA
Publication of US20100178374A1 publication Critical patent/US20100178374A1/en
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Assigned to SUMCO CORPORATION reassignment SUMCO CORPORATION MERGER (SEE DOCUMENT FOR DETAILS). Assignors: JAPAN SUPER QUARTZ CORPORATION
Expired - Fee Related legal-status Critical Current
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/10—Crucibles or containers for supporting the melt
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/09—Other methods of shaping glass by fusing powdered glass in a shaping mould
    • C03B19/095—Other methods of shaping glass by fusing powdered glass in a shaping mould by centrifuging, e.g. arc discharge in rotating mould
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
    • C30B35/002—Crucibles or containers

Definitions

  • This invention relates to a mold suitable for use in the production of a silica crucible used when producing a silicon single crystal ingot by a pulling method such as the CZ method or the like.
  • the invention is directed to advantageously reduce the amount of silica or quartz powder used when producing a silica crucible by a rotating mold method.
  • Such a silicon wafer is usually produced by forming a silicon single crystal ingot and then slicing it.
  • Such a silicon single crystal ingot is generally produced, for example, by a pulling method such as the CZ method or the like. Also, a silica crucible is used for pulling the silicon single crystal.
  • the rotating mold method is a method wherein silica or quartz powder is attached to an inner wall of a rotating mold, that is, a bottom surface and a side surface of the mold and then fused by heating (e.g., by arc heating) to produce a silica crucible.
  • the silicon single crystal ingot is desired to have a larger diameter in association with the rapid increase in the demand for silicon wafers.
  • the silica crucible to be used is also required to have a larger diameter.
  • a portion having a small outer diameter and a thin thickness (hereinafter referred to as a small-diameter thinned portion) occurs in an upper part of the silica crucible, and hence it is required to remove the small-diameter thinned portion by cutting.
  • the silica crucible When the silica crucible is heated to a high temperature in a step for filling and melting Si in the silica crucible to pull an Si single crystal, the viscosity of silica is reduced as the temperature rises and hence the silica crucible is easily deformed. Especially when the upper part of the silica crucible is the small-diameter thinned portion, it is apt to be fallen down inward and easily deformed.
  • a cause of forming such a small-diameter thinned portion is that heat easily escapes at the opening portion of the mold and the silica or quartz powder is not completely melted by arc heating, and hence the outer diameter at the upper part of the silica crucible becomes small and the thickness thereof becomes thin.
  • the formation of such a small-diameter thinned portion is unavoidable in the production process.
  • JP-A-2006-96616 proposes a silica glass crucible in which a ring-shaped member preferably made of carbon is embedded in the upper portion of the crucible.
  • a silica glass crucible can reduce the falling of the small-diameter thinned portion of the crucible inward.
  • the formation of the small-diameter thinned portion cannot be completely prevented. Therefore, it is still difficult to produce a good silicon single crystal ingot by the pulling method even when such a silica glass crucible is used.
  • this technique entails such a structure that a ring-shaped member made of a different material is embedded in a crucible, so that there is a fear that when a carbon ring is embedded in a silica glass, strain is caused due to the difference in the thermal expansion coefficient between both the members.
  • the silica crucible is produced by the rotating mold method, by anticipating the formation of the small-diameter thinned portion is produced a silica crucible having a crucible height higher by the small-diameter thinned portion than a height of a product specification and then the small-diameter thinned portion is removed by cutting to obtain a product.
  • silica crucibles having different heights may be produced in the same mold. Although there is no problem in the production of a silica crucible having a higher height, a portion to be removed by cutting becomes large in the production of a silica crucible having a low height. In order to solve the problem, a mold for exclusive use for a product having a low height may be provided, but when the number of silica crucibles produced is small or the like, there is a disadvantage that the production cost of a new mold and related costs become significant.
  • the formation of the small-diameter thinned portion is unavoidable, so that a silica crucible having a crucible height higher by the small-diameter thinned portion than a height of a product specification is produced and then the small-diameter thinned portion is removed by cutting to obtain a product (silica crucible) through usual steps.
  • the silica crucible is recently required to have a large diameter with the increase of the diameter of the silicon single crystal ingot as described above.
  • the diameter of the crucible is made larger, a portion obliged to be removed by cutting is also increased due to the small-diameter thinning, which causes a serious problem in terms of the material cost, and hence the production cost.
  • the invention is developed in the light of the above situation and is to provide a mold for producing a silica crucible capable of reducing a portion obliged to be removed by cutting due to the small-diameter thinning in the upper part of the silica crucible to effectively reduce the material cost.
  • a mold for use in the production of a silica crucible having an upper opening portion comprising: a cylindrical rim member; and one or more hooks, wherein the cylindrical rim member is engagedly supported through the one or more hooks to an inner side of the upper opening portion of the mold and, wherein an outer diameter of the rim member is smaller than an inner diameter of the mold but larger than an inner diameter of a silica crucible to be formed in the mold.
  • a mold for use in the production of a silica crucible according to item 1, wherein a protruding thickness t 1 of an inner surface of the cylindrical rim member from an inner peripheral wall of the mold, which is defined by t 1 (inner diameter of mold ⁇ inner diameter of rim member)/2, is 20 to 80% of a thickness t 2 of silica or quartz powder to be attached to the inner peripheral wall of the mold.
  • the hooks as a hanging jig of the invention can be used repeatedly.
  • FIG. 1 is a cross-sectional view illustrating a production manner of a silica crucible by a rotating mold method
  • FIG. 2 is a schematically cross-sectional view of a silica crucible produced using a commonly-used mold
  • FIG. 3 is a schematic view of a mold according to the invention, wherein ( a ) is an exploded view of the mold, ( b ) is a diagram showing a state of combining a rim member and a mold substrate, and ( c ) is a diagram showing a cutting of a small-diameter thinned portion;
  • FIG. 4 is a diagram showing a typical shape of a hook
  • FIG. 5 is a diagram showing a preferable embodiment of engagedly supporting a rim member through a hook.
  • FIG. 1 is schematically shown a typical production manner of a silica crucible by a rotating mold method.
  • numeral 1 is a mold
  • numeral 2 a vent pipe
  • numeral 3 arc electrodes and numeral 4 silica or quartz powder attached onto an inner wall of the mold 1 .
  • the mold 1 comprises a cylindrical straight body A, a cone-shaped bottom portion B and a corner portion C connecting them as shown in FIG. 1 .
  • the silica or quartz powder 4 attached onto the inner wall of the rotating mold 1 can be vitrified by fusing through arc heating and shaped into a crucible form.
  • FIG. 2 In FIG. 2 is shown a cross-sectional shape of a vitreous silica crucible 5 produced by using a commonly-used conventional mold.
  • the upper portion of the vitreous silica crucible 5 becomes smaller in the outer diameter and thinner in the thickness to form a small-diameter thinned portion 6 .
  • a cylindrical rim member is engagedly supported through hooks to the inner side of the upper opening portion of the mold so as to solve the above problem.
  • the invention is based on a technological idea that if an upper portion of a crucible becomes inevitably smaller in the outer diameter and thinner in the thickness in the production of the crucible, the mold for the crucible is preliminarily rendered into a shape corresponding to the shape of the upper portion of the crucible, whereby an amount of silica or quartz powder wastefully used can be reduced.
  • the invention is based on a technological idea that it is possible to recycle as a rim member a small-diameter thinned portion formed in the upper portion of the silica crucible during the production of the silica crucible and obliged to discard after being removed by cutting, whereby extra production cost is unnecessary.
  • numeral 7 is a rim member and numeral 8 is a hook as a hanging jig for the rim member 7 .
  • the rim member 7 can be newly produced separately. However, it is advantageous in terms of cost to recycle as a rim member a small-diameter thinned portion formed in the upper portion of the silica crucible during the production of the silica crucible and obliged to discard after being removed by cutting.
  • rim member can be used carbon having a barrier function against arc heating (thermal conductivity: about 140 W/mK, thermal expansion coefficient: about 5 ⁇ 10 ⁇ 6 /° C.).
  • a protruding thickness t 1 of an inner surface of the rim member from an inner surface of the mold is 20 to 80% of a thickness t 2 of silica or quartz powder attached to the inner surface of the mold.
  • a shrinkage percentage of silica or quartz powder is about 50 to 65%, and thus the thickness of the silica crucible is about 35 to 50% of the attached thickness of the silica or quartz powder. Therefore, when the protruding thickness t 1 of the inner surface of the rim member from the inner surface of the mold is 20 to 80% of the attached thickness t 2 of the silica or quartz powder, the inner diameter of the rim member may be larger than, nearly equal to or smaller than that of the silica crucible.
  • the inner diameter of the rim member is not particularly limited and there can be adapted a rim member having an inner diameter larger than, nearly equal to or smaller than that of the silica crucible.
  • the height H of the rim member 7 may be equal to the height of the small-diameter thinned portion.
  • the height of the small-diameter thinned portion is about 30 to 100 mm.
  • the thickness of the rim member 7 is not particularly limited, but is preferable to be about 5 to 15 mm.
  • the inner surface of the rim member has a surface roughness of about 6.3 to 25 ⁇ m as an arithmetic mean roughness Ra.
  • the carbon rim member When carbon having a barrier function against arc heating is used as a rim member, the carbon rim member can be used repeatedly because it is hardly consumed in one or two use.
  • FIG. 4 shows a typical shape of the hook 8 as a hanging jig for the rim member.
  • the shape of the hook 8 is not particularly limited and may be of any shape capable of stably supporting the rim member by hanging. However, since the hook needs to be disposed on an unmelted portion in the production of the crucible, that is, between an inner surface of the mold left at an unmelted state during the melting and an outer surface of the crucible, a thickness of a portion E in the hook is preferable to be less than that of the unmelted portion.
  • the thickness of the unmelted portion is usually about 3 to 15 mm, so that the thickness of the portion E is required to be equivalent to such a thickness of the unmelted portion.
  • a material for the hook is preferable to have load bearing properties and heat resistance even when the hook is thin and to be durable to multiple uses, which is typically exemplified by carbon (thermal conductivity: about 140 W/mK, thermal expansion coefficient: about 5 ⁇ 10 ⁇ 6 /° C.).
  • two to five hooks are disposed at equal intervals from a viewpoint that the rim member is supported stably by hanging. More preferably, the number of hooks is 3 or 4.
  • FIG. 5( a ) shows a basic form, in which an upper end portion of the hook 8 is locked on an upper surface of the mold 1 and thereafter the rim member 7 is engaged with a lower end portion of the hook 8 and then silica or quartz powder is filled so as to embed the rim member 7 therein.
  • FIG. 5( b ) shows a case of taking measures against the deterioration of the hook 8 , in which a groove hanging the hook 8 (whose width and depth correspond with or larger than the hook shape) is provided on the upper surface of the mold 1 so that the upper surfaces of the mold 1 , the hook 8 and the rim member 7 are so-called flush or the hook 8 is not projected from the upper surface of the mold 1 .
  • FIG. 5( c ) shows a case of taking further measures against the deterioration of the hook 8 , in which a groove having a size deeper than the upper end portion of the hook 8 is provided on the upper surface of the mold 1 to cover the upper surface of the hook 8 with silica or quartz powder.
  • the carbon hook is easily consumed through oxidation by contacting with oxygen at a high temperature, it is advantageous to suppress the contact with oxygen by providing the groove on the mold or covering the hook with silica or quartz powder as mentioned above.
  • the amount of silica or quartz powder reduced can be approximated by the following equation:
  • the amount of silica or quartz powder reduced can be calculated according to the weight of the rim member used as shown in Table. 1.
  • a rim member having a weight of 0.9 kg is disposed as shown in FIG. 5( a ). As a result, 0.5 kg of silica or quartz powder can be reduced.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Glass Melting And Manufacturing (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US12/688,452 2009-01-15 2010-01-15 Mold for producing silica crucible Expired - Fee Related US8066254B2 (en)

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JP2009006202A JP5100668B2 (ja) 2009-01-15 2009-01-15 石英ルツボ製造用モールド
JP2009-006202 2009-01-15

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100112115A1 (en) * 2008-10-31 2010-05-06 Japan Super Quartz Corporation Mold for producing a silica crucible

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5299252B2 (ja) * 2009-01-15 2013-09-25 株式会社Ｓｕｍｃｏ 石英ルツボ製造用モールド
JP5605902B2 (ja) * 2010-12-01 2014-10-15 株式会社Ｓｕｍｃｏ シリカガラスルツボの製造方法、シリカガラスルツボ
JP6941042B2 (ja) 2017-12-12 2021-09-29 信越石英株式会社 モールド及び石英ガラスるつぼの製造方法
JP7359734B2 (ja) 2020-04-06 2023-10-11 信越石英株式会社 成型板、石英ガラスるつぼの製造装置及び石英ガラスるつぼの製造方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3155479A (en) * 1960-05-25 1964-11-03 Owens Illinois Glass Co Centrifugal molds and method of forming hollow articles
JP2006096616A (ja) 2004-09-29 2006-04-13 Toshiba Ceramics Co Ltd シリカガラスルツボ、シリカガラスルツボの製造方法
US7160387B2 (en) * 2003-04-02 2007-01-09 Japan Super Quartz Corporation High purity silica crucible by electrolytic refining, and its production method and pulling method

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3011114B2 (ja) * 1996-01-12 2000-02-21 住友金属工業株式会社 シリコン溶融用坩堝
JP4279015B2 (ja) 2002-03-19 2009-06-17 コバレントマテリアル株式会社 石英ガラスルツボ及び石英ガラスルツボの製造方法
US20050120945A1 (en) 2003-12-03 2005-06-09 General Electric Company Quartz crucibles having reduced bubble content and method of making thereof
JP4863927B2 (ja) * 2007-04-27 2012-01-25 信越石英株式会社 シリコン単結晶引上用石英ガラスルツボおよびそれを使用したシリコン単結晶の製造方法
JP5102744B2 (ja) * 2008-10-31 2012-12-19 ジャパンスーパークォーツ株式会社 石英ルツボ製造用モールド
JP5286560B2 (ja) * 2009-01-15 2013-09-11 株式会社Ｓｕｍｃｏ 石英ルツボ製造用モールド
JP5299252B2 (ja) * 2009-01-15 2013-09-25 株式会社Ｓｕｍｃｏ 石英ルツボ製造用モールド

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3155479A (en) * 1960-05-25 1964-11-03 Owens Illinois Glass Co Centrifugal molds and method of forming hollow articles
US7160387B2 (en) * 2003-04-02 2007-01-09 Japan Super Quartz Corporation High purity silica crucible by electrolytic refining, and its production method and pulling method
JP2006096616A (ja) 2004-09-29 2006-04-13 Toshiba Ceramics Co Ltd シリカガラスルツボ、シリカガラスルツボの製造方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100112115A1 (en) * 2008-10-31 2010-05-06 Japan Super Quartz Corporation Mold for producing a silica crucible

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Publication number Publication date
US20100178374A1 (en) 2010-07-15
JP5100668B2 (ja) 2012-12-19
JP2010163312A (ja) 2010-07-29
KR101165984B1 (ko) 2012-07-18
KR20100084136A (ko) 2010-07-23

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